A new class of amperometric glucose sensor, in which electrical communication between the flavin redox centers of glucose oxidase and an electrode is achieved via a network of donor-acceptor relays chemically bound to a flexible siloxane polymer, has recently been invented in our laboratories. This biosensor may prove to be suitable for implantation since the electron transfer mediators are covalently attached to an insoluble polymer and cannot diffuse away from the electrode. The proposed research plan for Phase I concerns the development of this class of sensor through the following approach: (1) synthesis of a family of polymeric relay systems based on various ferrocene and quinone derivatives, which differ in oxidation potential and ability to reoxidize glucose oxidase, and a siloxane copolymer; (2) construction of carbon paste electrodes containing glucose oxidase and each of these new polymeric relay systems; (3) electrochemical testing of these biosensors using cyclic voltammetry and a constant potential procedure. Emphasis will be placed on determining the optimal electron transfer relay system based on the following considerations: sensitivity to glucose, low operating potential, insensitivity to oxygen, and long-term stability.